The ins and outs of decontamination

In the standard NZS8510:2017 for the testing and decontamination of methamphetamine-contaminated properties, it’s made clear how meth-testing and decontamination companies should communicate and work together.

To ensure there’s no conflict of interest between the sampling and decontamination of a property, meth-testing companies can in no way own or be financially involved with a decontamination company – and vice versa.

The practices and processes for sampling and decontamination are clearly defined and complimentary of each other. But we understand having to deal with a number of people and companies throughout the sampling and decontamination process, can sometimes be confusing.

Because we’re a meth-testing company, we can’t speak to or advise on the decontamination process. However, with an increase in demand for information on property decontamination, we've used our blog to do things a little differently.

Last month, we asked a number of decontamination companies to help us put together a list of FAQs for us to share with our clients.

If you’re a real estate agent or property manager, share this information with your clients. We hope it’s useful and helps to make the overall process easier to understand.

FAQs are based on sampling and decontamination processes and practices as per the standard NZS8510:2017.

Decontamination FAQs

In general, what is involved with decontamination?

The way in which a company decontaminates a property can differ depending on which company you use, however, as per the standard NZS8510:2017, the aim of decontamination is to reduce contamination levels to or below 1.5µg/100cm² in high use areas.

To do this, companies may use a variety of techniques including, but not limited to:

Triple cleaning, chemical treatment, ventilation and/or removal (if required) of certain building materials i.e. carpets, soft furnishings, absorbent materials and electrics, stained or varnished building materials, wallpaper, electrical appliances used for food preparation or cooking, ventilation systems like rangehoods.

How do testing and decontamination companies work together?

In the context of MTNZ as the meth-testing company, once we’ve completed sampling (including a screening and detailed assessment), any area found to be contaminated above 1.5µg/100cm² requires decontamination. It is up to you (the client) to determine which decontamination company to use.

A decontamination company would base their scope of works on MTNZ’s sampling report. Once the property has been sufficiently decontaminated, MTNZ would return to carry out post-decontamination sampling.

We would then provide the decontamination company, and you (the client) with a post-decontamination report, only once contaminated areas were below 1.5µg/100cm². The decontamination company can then provide you (the client) with a final report and clearance certificate.

What should I be looking for in a quote from a decontamination company?

  • Comprehensive scope of work
    Ensure quotes cover all contaminated areas, detailed scope of works including the decontamination process i.e. products to be used, treatment of specific building materials, and any anticipated damage, if any, that could be caused to the property based on a company’s proposed process.
  • Do your research
    Pay attention to how long a decontamination company has been operating, if they adhere to the standard NZS8510:2017 and worksafe practices, and how transparent they are with their decontamination process and client communication.

Ask for proof of work and pay attention to if a company has had to return to a property numerous times after post-decontamination sampling.

  • They are fully insured with public liability and any other insurances required for the industry.
  • Reinstatement costs
    Some quotes may appear cheaper than others so it is important to fully understand the differences and whether reinstatement costs (if required) are included.

What variables influence the price of decontamination?

  • Size of property and levels of contamination.
  • Surfaces and coatings including stained, varnished, absorbent, MDF based building materials, exposed beams or soft furnishings due to their ability to withstand the decontamination process.
  • Removal (if required) of wallpaper, carpets, electrics, food preparation and electrical appliances, and ventilation systems.
  • Property access.

Which building materials, if any, are difficult to decontaminate?

There are a variety of materials which can be difficult or challenging to decontaminate because of the way in which methamphetamine reacts:

  • Sealed surfaces i.e. polyurethane, enamel paint, varnish, shellac, stained material
  • Lockwood
  • Concrete
  • Recently painted surfaces
  • Rough sawn beams
  •  Michelangelo type ceiling tiles and chip board

How long does it take to decontaminate a property?

The decontamination process will generally take anywhere between a couple of days to a week. This timeframe excludes the additional time it will take for post-decontamination sampling and any follow-up decontamination required.

How do decontamination companies know when a property has been sufficiently cleaned, enough for the testing company to return?

Decontamination companies will use their knowledge and experience of building materials and contamination levels to determine whether a property is ready for post-decontamination sampling.

How often are properties ‘completely stripped’ and why would this need to happen?

The majority of rooms/properties can be decontaminated without needing to be completely stripped. There are a couple of things, which in extreme circumstances, may require a certain material to be stripped from a room or property (usually when contamination levels are high):

  • It can be more economical with some materials to replace rather than repair e.g. internal hollow core doors
  •  If contamination has been recently painted over encapsulating the contamination
  • If the contamination level is extremely high


Are there any risks associated with decontamination?

Risks can be mitigated by decontamination companies adhering to the standard NZS8510:2017 and worksafe practices for those working on a property during decontamination.

Decontamination companies should make you aware of any risks to your health and safety during decontamination.

How do I find out if a property has been decontaminated previously?

There are a couple of ways in which you can find out if a property has been previously decontaminated including:

  • Speak to the owners or tenants of neighbouring properties
  • Asking the owner for any recent sampling reports

What, if any, guarantees can decontamination companies provide clients?

Guarantees can be difficult for decontamination companies to provide, particularly with a lot of older New Zealand homes. However, all of the decontamination companies we spoke with said, as per the standard NZS8510:2017, the issue of a clearance certificate can only happen once decontamination levels are below 1.5µg/100cm². Majority of the companies we spoke with said they would be happy to return to a property, free of charge, to complete a job if contamination level requirements were not met.

What is needed for decontamination companies to provide a clearance certificate?

Once a property has been sufficiently decontaminated, the meth-testing company returns to carry out post-decontamination sampling. As per the standard NZS8510:2017, meth-testing and decontamination should meet the competencies required. Once the meth-testing company provides the decontamination company and property owner with a post-decontamination report that shows contaminated areas are below 1.5µg/100cm², the decontamination company can provide a final report and clearance certificate.

We hope this information will help clear up some of your questions on the process of decontamination. Should you have any further questions, please call us on 0800 34 34 33

Our thanks to the decontamination companies who have given us their valuable time and knowledge to provide answers to these questions.